Device for inducing motion to a joint



June 6,1967 H. M. SWANSON DEVICE FOR INDUCING MOTION TO A JOINT Filed April 10, 1964 INVENTOR HOWARD M. SWANSON ASSOCIATE ATTORNEYS United States Patent 3,323,518 DEVICE FOR INDUCING MOTION TO A JOINT Howard M. Swanson, 2261 Wyoming St., Salt Lake City, Utah 84109 Filed Apr. 10, 1964, Ser. No. 358,755 3 Claims. (Cl. 128-25) This invention has to do with a mechanical device for medical use, and more specifically with a device for inducing motion such as flexure in parts of the body.

While this invention is most importantly applied in connection with the human body, it is equally well suited for use in veterinary medicine, the need therefore and the principles involved being substantially the same. For the sake of simplicity, it will be described in terms of its application to human medicine.

It is well recognized that therapeutic treatment of the human body may require motion to be induced in a specific part, for example a knee-joint, for any of several reasons. Sickness, disease or nerve injury may have caused a reduction in bodily functions, or may have left the patient unable to voluntarily move and exercise the muscles adjacent to the joint. In such cases, induced motion may beneficially strengthen muscles, improve circulation and permit retention or restoration of the mobility of the joint.

Equally, the need for induced motion may arise because an earlier stage of medical treatment has intentionally reduced joint mobility. Such earlier treatment may for example have been associated with fracture of a bone or a joint; extensive laceration of skin or muscle tissue; or burns. In the course of treating such conditions, immobilization may have been required to permit healing. It is recognized that in such cases, however, excessive immobilization, involving too long a period of immobility, or immobility applied to too large a portion of the body, is highly undesirable. Such excessive immobility can lead to decreased circulation, lessened muscular activity, localized or general weakness, and even permanent loss of some articulation.

To avoid these dangers, planned and controlled motion in or adjacent to an affected part is a normal part of the medical treatment. In the past, such controlled motion has been provided by massage, by manual flexure of joints performed by a nurse, by limited exercise on the part of the patient, or by any of several devices described in the prior art. In general, such prior art mechanisms require a substantial exterior framework to which the patients arm or leg can be attached, and a reciprocating, rotating or vibrating means powered by a motor mounted on the framework. They require much storage space when not in use, and are inconvenient to move from one place to another.

There has been a need, therefore, for a simple, compact, light-weight reliable and easily controllable apparatus, by which a patients joint or other body part could be repeatedly flexed or otherwise appropriately moved.

Other types of induced body motion are also frequently required for therapeutic treatment, such as rotation of the lower arm, transverse motion of the thumb, and expansion and contraction of the chest cavity to promote respiration. Desirably, such an apparatus would not take up much space in use or in storage, would be usable directly at the patients bed, would simulate natural motion as closely as possible and would therefore use the patients own body as the natural fixed reference point for the motion of the moving part. Such an apparatus would desirably not require constant attention on the part of hospital staff or attendants, and should be easily adjustable as to rate and frequency of motion, extent of motion and duration of treatment. For the sake of safety,

3,323,518 Patented June 6, 1967 the moving parts of such an apparatus should be compact and capable of being shielded from contact with the patient himself or the clothes covering him.

The need for an improved therapeutic apparatus for inducing bodily motion has been met by the present invention, which consists, in its broadest terms of description, of the following elements:

(a) a transducer, capable of transforming rotational motion into reciprocating motion of the alternate extension and retraction type;

(b) means for affixing the opposed relatively extending and retracting portions of the transducer to selected portions of the patients body, so that alternate extension and retraction will effect the desired mo tion in the body part to be treated.

Auxiliary elements, appropriate to the most effective use of this invention, are a power source capable of supplying rotational motion, and a flexible power-transferring linkage between the said transducer and the said .power source. These auxiliary elements are preferably directly coupled to the transducer, and are part of the preferred embodiment of the invention.

FIGURE 1 is a perspective view of the device shown attached to the arm;

FIGURE 2 is a side view partly broken away, of the cylindrical reciprocator; and

FIGURE 3 is an enlarged view of the drive screw assembly.-

The exemplification of this invention in its broad description is shown in FIGURE 1. It consists of:

(a) An electric motor 1;

(b) A cylindrical reciprocator 2 described in detail below, and having a fixed housing 3 and an alternately extending and retracting arm 4;

(c) A flexible shaft 5, driven by the motor and driving the cylindrical reciprocator;

((1) Two means 6 and 7 for attaching the reciprocator to the patients body, one disposed above and the other below the joint 8 to be flexed, the one: being connected to the fixed housing and the other to the arm of the reciprocator.

The preferred embodiment of this invention is based on the use of the cylindrical reciprocator indicated in FIGURE 1. This portion of the apparatus provides most completely and compactly for the desired requirements of lightweight. ready adiustability and safety and strength.

The cylindrical reciprocator is shown in detail in FIG- URE 2. The fixed housing 3 consists of a cylindrical tubing 9 and bearing ends 10 and 11; contained Within the tubing is a drive screw 12 which has both leftand righthand threads and which is carried axially within the tubing between an end bearing in end 10, and a collar bearing in end 11. The drive screw shaft 13 extends through the collar bearing outside the fixed housing, and is provided with an axial bore 14 and set-screw 15 for the attachment of the flexible shaft. Also contained within the cylindrical tubing is a collar 16 fitting snugly but easily within the tubing, and surrounding the drive screw, with which it is engaged by a rotating pawl 17 described further below. The collar also rides on a guide rod 18 which parallels the drive screw and which prevents rotation of the collar. The two ends of the guide rod are fixed in the bearing ends 10 and 11.

The rotating pawl is retained within the collar in a radial boring which permits the engaging end 19 of the pawl to ride in the groove of the drive screw, while permitting the pawl to rotate in the boring so as to follow the groove angle at the reversal points of the drive screw. These reversal points, at the opposite ends of the screw, are formed by the intersection of the left-hand portion and the right-hand portion of the screw, forming a continuous path which the pawl can traverse. The outer extremity 20 of the pawl is flush with the surface of the collar, and is kept within the boring by contact with the inner surface of the cylindrical tubing. The inner extremity of the pawl is formed to a blunt double-chisel engaging edge wide enough to obviate jamming in the grooves of the screw at groove-intersection points.

Afiixed to the collar and extending parallel to the axis of the drive screw is the reciprocating arm 4 which passes through end and extends substantially beyond the fixed housing assembly. The arm terminates in a connecting device 21 for attachment to the patients body at one side of e.g. below, the joint in which motion is to be induced.

As the drive shaft rotates, the collar moves reciprocally back and forth over the length of the shaft, as a result of the engagement of the pawl with the grooves of the screw.

The fixed housing is attached to the patients body at the other side of, e.g., above, the joint concerned. The attachment to the body in this example is by means of casts, the connection of the reciprocating arm 4 and the fixed housing 3 being by means of pins inserted in the plaster of the casts. The reciprocal motion of the transducer, acting against the pins in the cast, causes cyclic flexing of the body joint as already described.

While FIGURE 1 shows the body attaching means 6 and 7 as separated elements, attached independently to the body, it will be understood that the two means can be flexibly joined together, as by a hinge, without departing from the essential inventive principle. Indeed, for some types of flexural motion, a hinged cast may be preferred for medical reasons.

One of the features of the present invention is the use of a transducer to bring about the desired flexure or other motion of a body part. Those skilled in the art will recognize the substantial improvement which has been achieved by the present choice of a particular type of transducer-namely that type which transforms rotary motion directly into reciprocating extension and retraction motion. No other type of transducer permits the same combination of flexibility, controllability, compactness and safety.

The compactness and flexibility of the transducer of the present invention also afford lightness, portability and low power-drain, rendering the present apparatus uniquely suitable for use on a patient in transit, or when remote from commercial power sources, and for application of multiple units without tiring the patient. The simplicity of the apparatus makes for ease of maintenance and repair. The present invention, therefore, provides a unique advance over the prior art, in which a critical selection of elements, not heretofore recognized as crucial, permits the realization of goals which have previously been only vaguely defined.

The superiority of the present critical selection of the type of transducer may be further illustrated by a brief listing of the advantageous alternatives which are encompassed within the scope of this invention, without departing from the basic concept thereof.

By employing a reciprocator of appropriate size, the present invention may be applied to any part of the body, including fingers, wrists, knees, hips, and neck. By proper selection of the length of the drive screw, the total dis placement of the reciprocating motion can be fully controlled. The fixed housing may be square or rectangular in cross section, rather than round, and in this case the guide rod may be eliminated. Motor speed may be varied by known means, to permit full control over the rate of fiexure. By appropriate positioning of the transducer, motion at right angles to the base of support can be effected, as, e.g., for causing fiexure of the wrist. A timing switch can be employed to determine the period of treatment. A voluntary switch for use by patient or attendant may be included. Other modifications and additions to the basic elements already described will be apparent to those skilled in the art.

The effectiveness of the present invention in achieving the results indicated depends on the use of a number of interrelated elements. While it is clear that not all of these elements are in themselves new, the combination thereof is both new and useful. Moreover, the combination of elements is far from obvious, and is superior to anything known in the art of therapeutic treatment as heretofore employed.

What I claim is:

1. A therapeutic apparatus adapted to impart alternating motions of flexion and extension to a joint of the body, comprising:

(a) a transducer with means for transforming rotational motion into reciprocating motion adapted to cause opposite ends of said transducer alternately to extend and retract relative to each other; and

(b) means for afiixing said opposite ends to selected portions of the patients body on opposite sides of said joint so that alternate extension and retraction Will effect the desired flexion and extension.

2. A therapeutic apparatus adapted to impart alternating motions of flexion and extension to a joint of the body, comprising:

(a) a power source supplying rotational motion;

(b) a transducer with means for transforming rotationa1 motion into reciprocating motion adapted to cause opposite ends of said transducer alternately to extend and retract relative to each other;

(e) a flexible power-transferring linkage between the power source and the transducer; and

(d) means for affixing said opposite ends to selected portions of the patients body on opposite sides of said joint so that alternate extension and retraction will effect the desired flexion and extension of said joint.

3. A therapeutic apparatus as described in claim 2 wherein said transducer includes a double-threaded screw.

References Cited UNITED STATES PATENTS 2,264,465 12/1941 Vollett 15250.26 X 2,861,565 11/1958 Lapierre 128-71 3,034,131 5/ 1962 Lent.

FOREIGN PATENTS 55,973 10/1912 Austria. 441,661 11/1948 Italy.

RICHARD A. GAUDET, Primary Examiner.

L. TRAPP, Assistant Examiner, 

1. A THERAPEUTIC APPARATUS ADAPTED TO IMPART ALTERNATING MOTIONS OF FLEXION AND EXTENSION TO A JOINT OF THE BODY, COMPRISING: (A) A TRANSDUCER WITH MEANS FOR TRANSFORMING ROTATIONAL MOTION INTO RECIPROCATING MOTION ADAPTED TO CAUSE OPPOSITE ENDS OF SAID TRANSDUCER ALTERNATELY TO EXTEND AND RETRACT RELATIVE TO EACH OTHER; AND (B) MEANS FOR AFFIXING SAID OPPOSITE ENDS TO SELECTED PORTIONS OF THE PATIENT''S BODY ON OPPOSITE SIDES OF SAID JOINT SO THAT ALTERNATE EXTENSION AND RETRACTION WILL EFFECT THE DESIRED FLEXION AND EXTENSION. 